The primary objective of the proposed study is to assess familial and peer support during childhood and early adolescence as predictors of girls' physical activity across ages 13 to 15 years. Research has consistently shown that levels of physical activity decline during adolescence and that adolescent girls are at particular risk of low levels of activity. Low levels of physical activity can place adolescents at risk for obesity and its associated health comorbidities. Little research, however, has examined factors that foster the achievement and maintenance of recommended levels of physical activity among adolescents. The proposed study adds on to a pre-existing 10-year longitudinal study of approximately 197 girls, examined across ages 5 to 15 years, and their parents (NIH HD 32973). To date, three waves of data have been collected at two year intervals for girls and their parents (i.e., when girls were 5, 7, and 9 years old) and data collection at age 11 is currently in progress. Questionnaires assessing parent and peer influence on physical activity, designed by the principal investigator, were included in the longitudinal project starting when girls were 9 years old. As part of the proposed study, an objective 7-day assessment of girls' physical activity (using accelerometers) will be added to the existing longitudinal project when girls are 13 and 15 years old. Based on the objective assessment of physical activity, girls who meet recommendations of 60 minutes of moderate activity a day at ages 13 AND 15 will be classified as maintainers. Girls who fail to meet recommendations at one or both ages will be classified as non-maintainers. Using this categorization and the currently existing data in the longitudinal study, the specific goals of the proposed study as follows: (1) To describe differences in physical activity (self-reported), physical fitness, and weight status across ages 5 to 13 years for maintainers and non-maintainer; (2) To assess familial and peer support during childhood and early adolescence as predictors of the likelihood of being a maintainer; and (3) To examine weight status, attitudes toward women in sport, enjoyment of activity, and perceived competence in physical activity as moderators of the relationship between familial and peer support and girls' physical activity. Such information is essential to designing effective prevention programs that promote recommended levels of physical activity during adolescence. [unreadable] [unreadable]